Pilot controlled solenoid valve

Abstract

A pilot controlled solenoid valve ( 1 ) includes a housing ( 2 ) having an inlet ( 3 ) and an outlet ( 4 ), a valve seat ( 5 ) between inlet ( 3 ) and outlet ( 4 ), a valve element ( 6 ) cooperating with the valve seat ( 5 ), and a solenoid arrangement ( 7 ) having a coil ( 8 ) and a moveable armature ( 9 ), wherein the valve element ( 6 ) is arranged between an inlet chamber ( 11 ) connected to the inlet ( 3 ) and a pilot pressure chamber ( 12 ) and includes a pilot channel ( 15 ) extending from the pilot pressure chamber ( 12 ) to the outlet ( 4 ), wherein the moveable armature ( 9 ) opens and closes an opening of the pilot channel ( 15 ) into the pilot pressure chamber ( 12 ) depending on magnetic forces produced by the coil ( 8 ). In such a valve noise should be kept small. To this end, pressure decreasing means are provided decreasing a pressure in the pilot pressure chamber ( 12 ) below a pressure downstream the valve seat ( 5 ) when the valve element ( 6 ) is lifted off from the valve seat ( 5 )), wherein the pressure decreasing means are driven by a flow of a fluid from the inlet ( 3 ) to the outlet ( 4 ) controlled by the valve and are in form of a flow restriction ( 17 ) in fluid connection with the pilot pressure chamber ( 12 ), wherein the flow restriction ( 17 ) is provided in addition to a flow restriction formed between valve element ( 6 ) and valve seat ( 5 ), wherein the flow restriction ( 17 ) includes a protrusion ( 16 ) of the valve element ( 6 ) protruding into the valve seat ( 5 ) when the valve element ( 6 ) is lifted off the valve seat ( 5 ) and a ring gap between the protrusion ( 16 ) and an inner wall of the outlet ( 4 ) is smaller than a distance between valve element ( 6 ) and valve seat ( 5 ) in a fully open condition of the valve, so that the area through which the fluid controlled by the valve ( 1 ) can pass is the smallest one on the way from the inlet ( 3 ) to the outlet ( 4 ).

What is claimed is: 
     
       1. A pilot controlled solenoid valve comprising a housing having an inlet and an outlet, a valve seat between inlet and outlet, a valve element cooperating with the valve seat, and a solenoid arrangement having a coil and a movable armature, wherein the valve element is arranged between an inlet chamber connected to the inlet and a pilot pressure chamber and comprises a pilot channel extending from the pilot pressure chamber to the outlet, wherein the movable armature opens and closes an opening of the pilot channel into the pilot pressure chamber depending on magnetic forces produced by the coil, wherein pressure decreasing means are provided for decreasing a pressure in the pilot pressure chamber below a pressure downstream the valve seat when the valve element is lifted off from the valve seat, wherein the pressure decreasing means are driven by a flow of a fluid from the inlet to the outlet controlled by the valve and are in form of a flow restriction in fluid connection with the pilot pressure chamber, wherein the flow restriction is provided in addition to a flow restriction formed between valve element and valve seat, wherein the flow restriction comprises a protrusion of the valve element protruding into the valve seat when the valve element is lifted a distance off the valve seat and a ring gap which is formed between the protrusion and an inner wall of the outlet in a fully open condition of the valve, wherein a width of the ring gap is smaller than the lift off distance between the valve element and the valve seat in the fully open condition of the valve, so that the area of the flow restriction in fluid connection with the pilot pressure chamber through which the fluid controlled by the valve can pass is the smallest one on the way from the inlet to the outlet; and that the valve comprises a second movable armature, wherein the movable armature and the second movable armature are arranged within a tube, wherein a spring is arranged between the two movable armatures, wherein the second movable armature is loaded by a second spring arranged between the second movable armature and a bottom of the tube, and wherein two pins are arranged between the second movable armature and the valve element for keeping a distance between the second movable armature and the valve element constant. 
     
     
       2. The valve according to  claim 1 , wherein the fluid connection is established via the pilot channel. 
     
     
       3. The valve according to  claim 1 , wherein the pilot channel runs through the protrusion. 
     
     
       4. The valve according to  claim 1 , wherein the valve element is in form of a piston. 
     
     
       5. The valve according to  claim 1 , wherein the valve element comprises a flow channel which is provided between the inlet chamber and the pilot pressure chamber and has a larger flow resistance than the pilot channel. 
     
     
       6. The valve according to  claim 5 , wherein the flow channel is arranged in the valve element and comprises a flow restriction. 
     
     
       7. The valve according to  claim 5 , wherein the valve element is provided with a piston ring sealing the inlet chamber against the pilot pressure chamber so that a fluid connection is possible only over the flow channel. 
     
     
       8. The valve according to  claim 1 , wherein the moveable armature is loaded by the spring in a direction towards the valve element. 
     
     
       9. The valve according to  claim 2 , wherein the pilot channel runs through the protrusion. 
     
     
       10. The valve according to  claim 2 , wherein the valve element is in form of a piston. 
     
     
       11. The valve according to  claim 3 , wherein the valve element is in form of a piston. 
     
     
       12. The valve according to  claim 2 , wherein the valve element comprises a flow channel which is provided between the inlet chamber and the pilot pressure chamber and has a larger flow resistance than the pilot channel. 
     
     
       13. The valve according to  claim 3 , wherein the valve element comprises a flow channel which is provided between the inlet chamber and the pilot pressure chamber and has a larger flow resistance than the pilot channel. 
     
     
       14. The valve according to  claim 4 , wherein the valve element comprises a flow channel which is provided between the inlet chamber and the pilot pressure chamber and has a larger flow resistance than the pilot channel. 
     
     
       15. The valve according to  claim 5 , wherein the valve element is provided with a piston ring sealing the inlet chamber against the pilot pressure chamber so that a fluid connection is possible only over the flow channel. 
     
     
       16. The valve according to  claim 6 , wherein the valve element is provided with a piston ring sealing the inlet chamber against the pilot pressure chamber so that a fluid connection is possible only over the flow channel. 
     
     
       17. A pilot controlled solenoid valve comprising a housing having an inlet and an outlet, a valve seat between inlet and outlet, a valve element cooperating with the valve seat, and a solenoid arrangement having a coil and a first movable armature,
 wherein the valve element is arranged between an inlet chamber connected to the inlet and a pilot pressure chamber and includes a pilot channel extending from the pilot pressure chamber to the outlet, 
 wherein the first movable armature opens and closes an opening of the pilot channel into the pilot pressure chamber depending on magnetic forces produced by the coil, 
 wherein a pressure decreasing means is provided for decreasing a pressure in the pilot pressure chamber when the valve element is lifted off from the valve seat and the valve is in a fully open condition, 
 wherein the pressure decreasing means is driven by a flow of a fluid from the inlet to the outlet controlled by the valve, 
 wherein the pressure decreasing means is a flow restriction provided when the valve element is in the fully open condition, the flow restriction including a ring gap which is formed between a protrusion protruding into the outlet and an inner wall of the outlet, 
 wherein a width of the ring gap between the protrusion and the inner wall is smaller than a lift off distance between the valve element and the valve seat in the fully open condition of the valve, so that an area of the ring gap is smaller than an area between the valve element and the valve seat in the fully open condition of the valve, 
 wherein the flow restriction formed by the ring gap results in a decrease of a pressure of a flow of the fluid at a downstream end of the protrusion as compared to the pressure of the flow of the fluid immediately downstream of the valve element and the valve seat in the fully open condition of the valve, and 
 wherein the decreased pressure is in fluid connection with the pilot pressure chamber. 
 
     
     
       18. The valve according to  claim 17 , wherein the solenoid valve further comprises a second movable armature, wherein the first armature and the second movable armature are arranged within a tube, wherein a spring is arranged between the two movable armatures, wherein the second movable armature is loaded by a second spring arranged between the second movable armature and a bottom of the tube, and wherein at least one pin is arranged between the second movable armature and the valve element for keeping a distance between the second movable armature and the valve element constant. 
     
     
       19. The valve according to  claim 17 , wherein the valve element comprises a flow channel which is provided between the inlet chamber and the pilot pressure chamber and has a larger flow resistance than the pilot channel. 
     
     
       20. The valve according to  claim 19 , wherein the valve element is provided with a piston ring sealing the inlet chamber against the pilot pressure chamber so that a fluid connection is possible only over the flow channel.